Ragnarok : the age of fire and gravel

CAUSED BY CONTINENTAL ICE-SHEETS? 37

away from each side of the valley of the Great Fish River, in north latitude €6°, of great height, and crowned with gigantic bowlders.

Why did not the advancing ice-sheet drive these deposits southward over the plains of the United States? Can we conceive of a force that was powerful enough to grind up the solid rocks, and yet was not able to remove its own débris ?

But there is still another reason which ought to satisfy us, once for all, that the drift-deposits were not due to the pressure of a great continental ice-sheet. It is this :

Tf the presence of the Drift proves that the country ia which it is found was once covered with a body of ice thick and heavy enough by its pressure and weight to grind up the surface-rocks into clay, sand, gravel, and bowlders, then the tropical regions of the world must have been covered with such a great ice-sheet, upon the very equator ; for Agassiz found in Brazil a vast sheet of “ferruginous clay with pebbles,” which covers the whole country, “a sheet of drift,” says Agassiz, “ consisting of the same homogeneous, unstratified paste, and containing loose materials of all sorts and sizes,” deep red in color, and distributed, as in the north, in uneven hills, while sometimes it is reduced to a thin deposit. It is recent in time, although overlying rocks ancient geologically. Agassiz had no doubt whatever that it was of glacial origin.

Professor Hartt, who accompanied Professor Agassiz in his South American travels, and published a valuable work called “The Geology of Brazil,” describes driftdeposits as covering the province of Pari, Brazil, upon the equator itself. The whole valley of the Amazon is coyered with stratified and unstratified and unfossiliferous